1. Field of the Invention
The present invention relates to a fuel injector for an internal combustion engine, more particularly to a fuel injector whose valve is opened and closed by a piezoelectric actuator.
2. Description of the Related Art
The faster a fuel injector can open and close its injecting port, that is, the faster a fuel injector can be actuated, the more accurately the fuel injector can be controlled and the more efficiently an engine having the fuel injector can be operated. Conventional solenoid actuators for opening and closing an injecting port take more than 1 msec for response. Piezoelectric actuators offer faster response, but have the drawback of insufficient valve lift.
The present inventors previously proposed a fuel injector offering both the fast response of a piezoelectric actuator and a sufficient valve lift in Japanese Patent Application No. 58-3637, which was laid open Nov. 22, 1984 under No. 59-206668 and hence is not "prior art" hereto. In this fuel injector, however, an excessively large load is applied on the actuator when the fuel supply pressure is very large. Therefore, this fuel injector cannot be made sufficiently compact.